Actually, a lone sentry is not beyond the realm of the possible. He may be "lone" insofar as the rest of his platoon may be in a dug in defensive position 30-50 metres behind him. He's there for early warning.

As I often joke when doing these type exercises (alas, in my past now), "who do I like least, you, you are on sentry."

Actually, a lone sentry is not beyond the realm of the possible. He may be "lone" insofar as the rest of his platoon may be in a dug in defensive position 30-50 metres behind him. He's there for early warning.

As I often joke when doing these type exercises (alas, in my past now), "who do I like least, you, you are on sentry."

The sentry may be "alone" at his post, but he wouldn't be "sent out to block a road" alone is my point. The fact you say his plattoon would be dug in a short distance (at least within gun shot range) away reinforces this.

It's not like you're telling one guy "Take your gun, go south and block Highway 31 to all military traffic coming north! Hold on as long as you can, until bullets or bodies run out!"

Now, I don't know much about the inside of a tank, but I can imagine one more scenario:

He managed to land a shot in the barrel when the breech was open. The shot went into the tank, possibly hitting the loader and causing some major confusion, possibly destruction of something important. Someone else (commander?) takes over, and mess up somehow (perhaps not sealing the breach properly?). Things go boom.

There are a couple of plausible scenarios where this could have happened. It all hinges on the type of vehicle which the soldier was facing. One thing that really defines this, is the fact that many tracked vehicles in WW2 were called "tanks" even though by modern definition they wouldn't be so.

I'm going to posit a scenario where the story becomes plausible, all based off of real vehicles which were often classified as tanks, and include in with them an armament for the soldier which makes sense.

During WW2, Germany used a number of mobile artillery types (often called Sturmgeweher (StuG), with varying calibers and capabilities. Note: This does not just apply to the "StuG" type of vehicle, but the term was a blanket term applied to all assault guns designed to support infantry advances. It is possible that the soldier, in the "right place at the right time" is facing against one of these vehicles. For this, the soldier is not "alone" per se, but part of an anti tank group equipped with a Boys anti tank rifle. (.50 cal solid steel AP rounds.)

In this scenario, the soldier guarding the road is expecting to come in contact with light vehicles (which the Boys could handle quite well), only to have a German SPG/assault gun come trundling down the road. Knowing that the casement or armor area of the SPG's are relatively weak, the soldier aims for this. However his shot misses, and travels into the gun's barrel. It does not strike an actual round, but instead impacts the breech block of the vehicle, damaging it. This goes unnoticed inside the vehicle, other than a loud "Spang" where the hit is. Given the noise inside the vehicle, the exact nature of the hit isn't known.

Spotting nearby infantry (nearby being a relative term), the commander orders a High Explosive round run into the breech. The loader complies, and closes the breech of the gun. The loader does not notice, or realize that the breech block has failed to fully close due to the damage it sustained; or the breech block has cracked at some point thanks to the round striking it.

When the gunner fires, the weakened breech is unable to withstand the forces of the propellant to fire the round, and in doing so fails. This causes the block to explosively blow into the tank, allowing the full force of the round in the barrel to blow back as well. The resulting explosion (in a confined area) incinerates most of the crew, starts fires, and causes stored ready ammunition, and fuel to explode; destroying the vehicle.

The above scenario is not limited simply to Assault guns though. This is a reasonable scenario for really any vehicle above a 50mm caliber (with 75 and above being more plausible) due to the opening size of the barrel, and the various weak points. It's worth noting that to those outside the vehicle, it would seem that the infantry man struck a round in the barrel, causing the explosion, as opposed to causing a breech block failure. Furthermore, it's reasonable to suspect a soldier with a relatively obsolete anti tank rifle would be aiming at the mantlet/casement of the gun, since if his aim was good enough he might expect to damage the elevation ability of the weapon, pierce gunner sights, or in the case of rounded mantlets like the Panther ausf. D, and some of the Panzer IV variants, cause the round to riccochet down off the gun and through the lightly armored deck of the tank. This riccochet being enough to strike and kill enemy crew, or cause further damage. Lastly, he might have sighted in on the turret ring, another weak point which would disable the vehicle, or at the very least make it unable to return fire.

My husband and I recently rented a WWII movie called "Fury". It starred Brad Pitt and Shia LaBeouf (among others), and this was one of the scenarios in the movie. I also found online a story/memoir by a man named Bill Betts who served in WWII on a tank and he was critiquing the Fury movie. Here's the link to his story: